1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) technology, more particularly to a method for setting gray levels of pixels of LCD panels.
2. Description of the Prior Art
LCD devices, being small, light, and with high display quality, have gradually replaced cathode ray tube (CRT) displays. An LCD panel is constructed by pixels arranged in matrices. Each pixel is constructed by subpixels that show colors, e.g. the red subpixel, the green pixel, and the blue subpixel. Brightness of each subpixel is determined by its own gray level as well as brightness of the panel's backlight module. The most common display method, however, is to keep the latter at a constant level while rotating, based on the image data input, the liquid-crystal molecules of each subpixel by various gray-level voltages. The rotation angles can then determine transparency of each subpixel, and thus determine its gray level in display.
As application of LCD devices broadens, a wider viewing angle is demanded, thus bringing to market such products, e.g. MVA LCD. This kind of LCD applies wide-angle image display via 2D1G technology, white balance technology, and so on. Please refer to FIG. 1 illustrating the structure of pixels on an LCD panel using 2D1G technology. The pixels include red subpixels, green subpixels, and blue subpixels. Each of the subpixels contains a main subpixel region and a secondary subpixel region. As shown in FIG. 1, upon receiving image data, the 2D1G technology is used to impose respective gray-level voltages on the main and secondary subpixel regions of each of the subpixels, in order that the pixels can display respective levels of brightness. Then, the white balance technology is used to impose respective gray-level voltages on each of the subpixels, in order that the pixels can display respective levels of whiteness. However, after the white balance process, the result of the former 2D1G process is usually affected. The gamma curve of each of the subpixels does not fit perfectly anymore in the gamma value 2.2, thus leading to phenomena such as color shift and light leakage in wide-angle displays.